Rubbing machine



y 1942- G. H. EKSTROM 2,282,043

RUBBING MACHINE Filed Nov. 8, 1939 UNITED STATES PATENT OFFICE RUBBINGMACHINE Gustaf H. Ekstrom, Rockford, Ill., assignor to SundstrandMachine Tool (30., Rockford, Ill a corporation of Illinois ApplicationNovember 8, 1939, Serial No. 303,354

19 Claims.

The present invention relates to a rubbing machine and more particularlyto the rubbing shoe thereof.

Among the objects of the invention is to provide a novel and improvedrubbing shoe having novel means for securely holding the abrasive sheetin place, such securing means affording a convenient, quick, and readyattaching and detaching of the abrasive sheet, with or without provisionfor making the shoe generally flexible for self-accommodation to theparticular contour or shape of the surface being treated or operatedupon.

Another object is to provide in a shoe of the character disclosed anovel clamping means which may be locked open for the removal and/ orthe insertion of the end of the abrasive sheet to be removed and/orclamped, and readily unlocked to effect the clamping function.

A further object is to provide in a clamp in a shoe of the characterdisclosed a clamp operating element which is a permanent part of theclamp and which avoids the need of using a separate tool or the likethat would easily become misplaced or lost.

Other objects, advantages, capabilities, features, and the like arecomprehended by the invention, as will later appear and as areinherently possessed by the invention.

Referring to the drawing:

Fig. 1 is a perspective view of a rubbing shoe embodying the invention.

Fig. 2 is a fragmentary top plan View at an end of the device.

Fig. 3 is an end view in elevation of the inven- I tion.

Figs. 4, 5 and 6 are side views in elevation of a clamp end portion ofthe device showing different steps of the use of the device.

While the invention is susceptible of various modifications andalternative constructions, the embodiment shown in the drawing anddescribed hereinafter is by way of preferred illustration only, and itis not intended that the invention be limited thereto or thereby, but iti intended to cover all modifications and alternative construc tionsfalling within the spirit and scope of the invention as defined by theappended claims.

Referring more in detail to the drawing, the embodiment chosen toillustrate the invention is shown as comprising a shoe having a pad I,such as felt, a flexible plate 2, which is preferably made of any kindof resilient material, surmounting the pad I and suitably attachedthereto as by an adhesive, transverse yieldable pad elements 3, such asrubber or the like, on the plate 2 and suitably attached thereto, as byan adhesive, and an upper flexible plate 4, which also is preferablymade of any kind of resilient material, surmounting the pads 3 andsuitably attached thereto, as

by an adhesive. Over the lower surface of the pad I extends an abrasivesheet 5, such as sandpaper or the like, with the end portions of thesheet extending about the ends of the pad I and clamped in novelclamping means hereinafter described.

The novel clamping means comprises a pair of clamps, one at each end ofthe shoe andboth being identical in structure and function. Eachclamping means comprises a transverse base plate 6 secured by rivets 1to an end portion of the plate I, with a portion 8 of the plate 4extending a short distance outwardly beyond the plate 6 as clearly shownin Figs. 4, 5 and 6.

The resilient part 9 of the clamp is in the form of a curved sheet, suchas spring steel, to form approximately a hollow cylinder with alongitudinal opening for the jaws I0 and I I of the clamp. The portionI0 forms the relatively stationary or still jaw part of the clamp and isrigidly secured to the top of the plate Ii by the rivet I, as shown,this jaw I0 having outwardly extending teeth or serrations I2. Theportion II forms the relatively movable or live jaw part of the clamp,which when in clamping or closed position and condition forcibly clampsthe end portion I3 of the abrasive sheet against the serrated jaw I0.The lip edge portion I4 of the jaw II is of such extent as to enter thespace I5 to put a crimp I6 in the end portion I3 of the abrasive sheet.

Within the part 9 and extending longitudinally thereof is anchored, onthe top of the jaw II] by way of the rivets I, a locking cam memberhaving an upwardly inclined cam part I! the upper edge of which may acta an abutment for the back portion of the spring part of the clampmember 9, as shown in Fig. 4. Also extending longitudinally within thepart 9 is a key plate I8 the ends of which extend without the endopenings of the part 9 and have upwardly extending arms I9 to the upperends of which is secured a rod or bar 20 by which the key may bemanipulated as later described.

The outer edge of the key plate I8 bears or fulcrunis against the innersurface of the jaw portion I I of the part 9 and has lugs 2I extendingthrough aperture 2| provided in the jaw portion II, these lugsacting aspivot elements when the key is operated. The inner edge portion of thekey plate has a lip 22, preferably rounded as shown, to bear against andslide over the outer surface of the cam H. In Figs. 1, 4 and 6, the lip22 is shown at the upper portion of the cam I1, at which time the clampis unlocked and is inclamping condition, and in Fig. 5 is shown at thelower portion of the cam IT, at which time the clamp is in locked andopen condition, the jaw being held wide openfor the 'free withdrawal ofthe end portion of the worn abrasive sheet and for the free insertion ofthe end portion of the new abrasive sheet.

The shoe is designed to be connected to a rubbing machine having powermeans for actuating the shoes. Therefore, provision is made for theoperative connection or attachment of the shoe to such machine, and thedevice herein disposition shown in Fig. 4 to the position shown in Fig.5, the lugs 2! acting to raise and open the jaw I! with what may betermed a toggle action. When the lip reaches its lowermost position, ithas passed what may be termed dead center so that the spring force ofthe jaw ll acting against the outer edge of the plate 58 is in adirection tending torock the plate upwardly about the line of contact ofthe lip 22 and cam II as an axis or fulcrum, thus'holding the clamplocked in open condition. The. user may then easily and quickly removethe worn abrasive sheet and replace it with a new sheet with the endportions 23 into the openings between the jaws of the clamps andopposite the spaces l5, as shown in Fig. 5. Then by pressing upwardlyand outwardly on the bar 2b, the lock is released and the jaws clampwith a snap to clamp the end portion of the abrasive sheet between thejaws It] and H, and to form the crimp 16 in the space l5 between theserrated portion 12 of the jaw It and the plate extension 8, as shown inFig. 6. During the unlocking action, the lip 22 slides upwardly over thecam ll, partly under the spring force of the jaw portion H and partlyunder the force applied by the user on the bar 253, to the position andrelation shown in Fig. 6. It will-be noted, as shown in Figs. 4, 5 and6, that the'cam I! is disposed in the position of a chord of the circleof the clamp body 9 diametrically opposite the jaw portion I! so thatwhen the key [8 is moved to "cause its rear edge to slide over thesurface of the cam 11 it will be made to pass by the line perpendicularto the cam II, which may be termed the dead center of the device.

Both the plates 2 and 4' are bendable or yieldable, so that as the shoeis applied to a contoured surface to be treated these plates will bendor .and not positive, there is always danger of the clamp prematurelysnapping closed and injuring the other hand which is manipulating theabrasive sheet. By the present invention, after the clamps have beenlocked open, both of the users hands'are free to safely manipulate theabrasive sheet without any danger of injury to either hand.

Also in devices using clamps wherein the means for opening theclamp is atool or the like which normally is free and independent, and is appliedonly at the time when the clamp is to be opened, such tool or element'is easily lost or misplaced, often making it necessary to search for itwith resultant loss of time. Moreover, there is a certain amount of timeand care required to connect the tool to the clamp so that it will notslip out and cause injury to the user. In the present invention, theclamp opening or operating means is a permanent part of the clampingmeans, being a rigid part of the looking key member shown in theembodiment selected to illustrate the invention.

I claim as my invention:

1. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe, in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means comprising astill jaw secured to the plate, a live jaw, and a resilient portionconnected between said jaws, a cam element located in fixed relation tothe still jaw, and a key member fulcrumed against the live jaw andcontacting the cam for sliding over said cam when the key member isforcibly rocked to move past dead center in the nature of a toggleaction so as to open the jaws and hold them locked in open condition.

7 2. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe, in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means comprising astill jaw secured to the plate, a live jaw, and a resilient portionconnected between said jaws, a cam element located in fixed relation tothe still jaw, and a key member iulcrumed against the live jaw andcontacting the cam for sliding over said cam when the key member isforcibly rocked to move past dead center in the nature of a toggleaction so as to open the jaws and hold them locked in open condition,said still jaw having a clamping lip and said plate having an endportion spaced from said lip to provide a crimping space therebetween,and said live jaw having a lip adapted to extend into said space to formtherein a crimp in the end portion of the abrasive sheet when beingclamped between said jaws.

3. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe, in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means compris inga sheet of spring material approximately in the form of a hollowcylinder withan elongated opening along a side thereof, one of the sideportions of said sheet at said opening constituting the still jaw of theclamp and being rigidly secured to an end portion of said plate, theother of said side portions constituting the live jaw of the clamp andbeing normally in clamping contact with the still jaw under theresilient force of the remainder of said spring sheet, a lock cam memberlocated within said spring sheet and secured at its lower portion tosaid still jaw and having an upwardly extending inclined cam portion.locking key located within said spring sheet and having its outward edgefulcrumed against said live jaw and its inward edge in contact with saidinclined cam portion, and

an arm secured to said key for rocking said key about its fulcrum and tocause said key at its inward edge to slide along said cam for openingthe jaws and for holding said jaws open.

4. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe, in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means comprising asheet of spring material approximately in the form of a hollow cylinderwith an elongated opening along a side thereof, one of the side portionsof said sheet at said opening constituting the still jaw of the clampand being rigidly secured to an end portion of said plate, the other ofsaid side portions constituting the live jaw of the clamp and beingnormally in clamping contact with the still jaw under the resilientforce of the remainder of said spring sheet, a lock cam located withinsaid spring sheet in fixed relation to said still jaw and disposed inthe position of a chord of the circle of the spring sheet inwardlyopposite said live jaw, a locking key extending between said live jawand said cam with the outward edge of the key fulcrumed against the livejaw and its inward edge in slidable contact with said cam, and an armrigid with said key for manual rocking of the key about its fulcrum atthe outward edge thereof and the sliding of said key at its inward edgeover said cam so as to pass by the line perpendicular to said chordposition of said cam for locking and holding locked said jaws in openposition.

5. A rubbing shoe of the character disclosed comprising spaced plates offlexible material, yieldable pads between said plates, and a cushion padat the outside of one of said plates, clamping means connected at theends of the other of said plates for clamping the ends of an abrasivesheet comprising spaced plates of flexible material, 3

yieldable pads between said plates, and a cushion pad at the outside ofone of said plates, clamping means connected at the ends of the other ofsaid plates for clamping the ends of an abrasive sheet extending overthe said cushion pad, said plates being flexible for the shoe to beself-accommodating to the contour of the surface being operated upon bythe shoe, each of said clamping means comprising a still jaw secured tothe plate, a live jaw, and a resilient portion connected between saidjaws, a cam element located in fixed relation to one of said jaws, and akey member fulcrumed against the other of said jaws and contacting thecam for sliding over said cam when the key member is forcibly rocked tomove past dead center in the nature of a toggle action so as to open thejaws and hold them locked in open condition.

7. A rubbing shoe of the character disclosed comprising spaced upper andlower resilient and flexible plates, yieldable and resilient padsbetween said plates, a yieldable cushion beneath said lower plate overwhich extends an abrasive sheet with its ends extending about andupwardly at the ends of the shoe, clamping means connected to the endsof the upper plate to clamp said ends of said abrasive sheet, saidplates being flexible for the shoe to be self-accommodating to thecontour of the surface being operated upon by the shoe.

8. A rubbing shoe of the character disclosed comprising spaced upper andlower resilient and flexible plates, yieldable and resilient padsbetween said plates, a yieldable cushion beneath said lower plate overwhich extends an abrasive sheet with its ends extending about andupwardly at the ends of the shoe, clamping means connected to the endsof the upper plate to clamp said ends of said abrasive sheet, saidplates being flexible for the shoe to be self-accommodating to thecontour of the surface being operated upon by the shoe, each of saidclamping means comprising a still jaw secured to the plate, a liv jaw,and a resilient portion connected between said jaws,a cam elementlocated in fixed relation to one of said jaws, and a key memberfulcrumed against the other of said jaws and contacting the cam forsliding over said cam when the key member is forcibly rocked to movepast dead center in the nature of a toggle action so as to open the jawsand hold them locked in open condition.

9. A rubbing shoe of the character disclosed comprising spaced upper andlower resilient and flexible plates, spaced and transversely extendingyieldable and resilient pads between said plates, a yieldable cushionextending over the lower face of said lower plate over which an abrasivesheet extends with its ends extending about and upwardly at the ends ofthe shoe, clamping means connected to the ends of the upper plate toclamp said ends of said abrasive sheet, said plates being flexible forthe shoe to be self-accommodating to the contour of the surface beingoperated upon by the shoe.

10. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe, in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means comprising astill jaw secured to the plate, a live jaw, and a resilient portionconnected between said jaws, a cam element located in fixed relation toone of said jaws, and a key member fulcrumed against the other of saidjaws and contacting the cam for sliding over said cam when the keymember is forcibly rocked to move past dead center in the nature of atoggle action so as to open the jaws and hold them locked in opencondition, said jaw against which said key is fulcrumed being providedwith an aperture and said key member having a projection extendingthrough said aperture to provide for pivotal connection between the keymember and said latter jaw.

11. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe, in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means comprising astill jaw secured to the plate, a live jaw, and a resilient portionconnected between said jaws, a cam element located in fixed relation toone of said jaws, and a key member fulcrumed against the other of saidjaws and contacting the cam for sliding over said cam when the keymember is forcibly rocked to move past dead center in the nature of atoggle action so as to open the jaws and hold them locked in opencondition. y

12. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe, in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means comprising astill jaw secured to the plate, a live. jaw, and a resilient portionconnected between said jaws, a cam element located in fixed relation toone of said jaws, and a key member fulcrumed against the other of saidjaws and contacting the cam for sliding over said cam when they keymember is forcibly rocked to move past dead center in the nature of atoggle action so as to open the jaws and hold them locked in opencondition, said still jaw having a clamping lip and said plate having anend portion spaced from said lip to provide a crimping spacetherebetween, and said live jaw having a lip adapted to extend into saidspace to form therein a crimp in the end portion of the abrasive sheetwhen being clamped between said jaws.

13. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe, in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means comprising astill jaw secured to the'plate, a live jaw, and a resilient portionconnected between said jaws, a cam element located in fixed relation toone of said jaws, a key member fulcrumed against the other of said jawsand contasting the cam for sliding over said cam when the key memberisforcibly rocked to move past dead center in the nature of a toggleaction so as to open the jaws and hold them locked in open condition,said still jaw having a clamping lip and said plate having an endportion spaced from said lip to provide a crimping space there- :25

between, and said live jaw having a lip adapted to extend into saidspace to form therein a crimp in the end portion of the abrasive sheetwhen being clamped between said jaws, and an arm secured to said key forrocking said key about its fulcrum and to cause said key at its otheredge to slide along said cam for opening said jaws and for holding saidjaws open.

14. In a rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with the ends thereof extending aboutthe ends of the shoe,.in combination, a clamping means for the abrasivesheet secured to each end of the plate, said clamping means comprising astill jaw secured to the plate, a live jaw, and a resilient portionconnected between said jaws, a cam element located in fixed relation toone of said jaws, a key member fulcrumed against the other of said jawsand contacting the cam for sliding over said cam when the key member isforcibly rocked to move past dead center in the nature of a toggleaction so as to open the jaws and hold them locked in open condition,said still jaw having a clamping lip and said plate having an endportion spaced from said lip to provide a crimping space therebetween,and said live jaw having a lip adapted to extend into said space to formtherein a crimp in the end portion of the abrasive sheet when beingclamped between said jaws, and an arm secured to said key for rockingsaid key about its fulcrum and to cause said key at its other edge toslide along said cam for opening said jaws and for holding said jawsopen, said other of said jaws being provided with an aperture and saidkey member having a projection extending into said aperture to providefor pivotal connection between said key and said other of said jaws.

l5. Ina rubbing shoe of the character disclosed having a plate overwhich an abrasive sheet extends with an end portion thereof extendingabout the end of the shoe to a clamping means, in combination, aclamping means comprising a pair of separable jaws and a resilientportion therebetween for normally closing said jaws, a cam elementlocated in fixed relation to one of said jaws, and a key memberfulcrumed against the other of said jaws and contactingthe cam forsliding over said cam when the key member is forcibly rocked to movepast dead center in the nature of a toggle action so as to open saidjaws and hold them locked in open condition.

16. In a rubbing shoe having a plate over which an abrasive sheet isdisposed with an end portion thereof extendin about each end of the shoefor securement, in combination, a clamping means on each end of saidplate comprising a pair of jaws with resilient means normally closingsaid jaws for gripping one end of the sheet between them, and a keymember manually adjustable to a position in which it braces the jawsopen in opposition to the resilient means, together with detent meansholding said key member in such bracing position.

17. In a rubbing shoe having a plate over which an abrasive sheet isdisposed with an end portion thereof extending about each end of, theshoe for securement, in combination, a clamping means on each end ofsaid plate comprising a pair of jaws with resilient means normallyclosing said jaws for gripping one end of the sheet between them, andmanually operable locking means adjustable to lock the jaws in openposition in opposition to said resilient means.

18. In a rubbing shoe having a plate over which an abrasive sheet isdisposed with an end portion thereof extending about each end of theshoe for securement, in combination, a clamping means on each end ofsaid plate comprising a fixed jaw and a movable jaw with resilient meansnormally urging the movable jaw into gripping relation to the fixed jawfor engaging one end of the sheet between them, a key member rockablyengaged with the movable jaw at a distance back of its gripping edge anda fixed detent surface with which said key member is engageable at aposition in which it braces the movable jaw open with the resilientmeans acting to hold the key engaged with the detent surface.

19. In a rubbing shoe having a plate over which an abrasive sheet isdisposed with an end portion thereof extending about each end of theshoe for securement, in combination, a clamping means on each end ofsaid plate comprising a fixed jaw and a movable jaw with resilient meansnormally urging the movable jaw into gripping relation to the fixed jawfor engaging one end of the sheet between them, a key member rockablyengaged with one of said jaws at a distance back of its gripping edgeand a detent surface at a distance back of the gripping edge of theother jaw formed to engage and retain said key member at a position inwhich it braces the jaws open, the resilient means acting to hold thekey engaged with said detent surface.

GUSTAF H. EKSTROM.

